1. Field of the Invention
The present invention relates to liquid level measuring devices, and more particularly to such devices which are constructed so that they can be adjusted for the different conditions met when installing the devices in differently constructed tanks and other liquid containers.
2. Description of the Prior Art
The prior art related to liquid level measuring devices discloses such devices which are capable of adjustment in their configurations for use in tanks and other containers having various wall orientations, volumes, sizes and shapes. For example, U.S. Pat. No. 1,141,500 discloses a liquid level measuring device mountable within a container in two different modes. The first mode, which we will refer to as a "top reading" mode, involves the mounting of an indicator in the top wall of a liquid container with the remainder of the device extending downwardly toward the liquid in the bottom of the container. In another mode, which we will call the "end reading" mode, the indicator is mounted in a side wall of a liquid container and the remainder of the device extends inwardly and downwardly into the liquid in the container. Other forms of top and end reading liquid measuring devices are disclosed in U.S. Pat. Nos. 1,286,953 and 1,448,842. The prior art, exemplified by the cited U.S. patents, has recognized the practical and economic advantages of providing liquid level measuring devices which can be adjusted for use in tanks or containers having various sizes and orientations. One such advantage is that the user has a multipurpose device for use in a variety of situations rather than having an individual measuring device for each tank size and orientation.
In recent years, various governmental and private organizations have developed uniform specifications for liquid shipping and storage drums. For example, there are specific standards for the so-called 30 and 55-gal. "Tight-Head Universal Drums". One such specification is D.O.T. Specification 17E, published in the Code of Federal Regulations Title 49, Part 178. Thus, the containers frequently found in industrial use will conform to one or more uniform specifications. It should be apparent, for example, that an industrial user may have numerous 55-gal drums on hand holding an inventory of liquids. Moreover, a user may have a number of 30-gal. drums on hand to hold an inventory of liquids. As to each of these types of containers, it may be that the user will store them in one of two types of orientations. First, one type of orientation is to lay the drums on their sides and to stack drums on top of each other with all of the axes of the drums running in one direction and the openings in the drum heads all facing the same direction. Another type of storage orientation is to have all of the drums together in a vertical orientation with the openings in the drum heads being at the top. In order to measure the liquid level in any drum, the user would need a top reading liquid level measuring device when the drums are vertically oriented and an end reading liquid level measuring device when the drums are in a horizontal storage configuration.
Certain disadvantages may be encountered when the prior art liquid level measuring devices are used in connection with the 30, 40, 55, etc. gallon drums now in widespread use. For example, standard 30 and 55-gal. drums have diametrically opposed openings in the drum head, one opening being a 3/4" fitting and the other opening being a 2" fitting. Thus, when a drum is used in a vertical orientation, one opening is utilized for the insertion of a means to withdraw the liquid from the drum and the other opening is available for the insertion of a liquid level measuring device. Thus, the liquid removal device and liquid level measuring device utilized in this situation must be compatible from the standpoint of the interior space utilization of the drum. Moreover, the size of the liquid level measuring device must conform to one of the standard openings. Thus, one dimension of the liquid level measuring device cannot exceed 2" in diameter thereby requiring a compact design.